Orthopedic procedures for the replacement of all, or a portion of, a patient's joint typically require resecting (cutting) or reshaping the ends of the bones forming the joint. For example, total knee arthroplasty (“TKA”) procedures typically include cutting open the knee, displacing the patella, resecting bone from the distal end of the femur, and resecting bone from the proximal end of the tibia to prepare the joint for prosthetic femoral and tibial implant components. Resecting the distal end of the femur often involves making one or more cuts including a planar distal cut. Resecting the proximal end of the tibia often involves making a planar proximal cut. In view of the foregoing surgical steps, TKA procedures are invasive but typically effective.
TKA procedures can be complicated by the fact that a mechanical axis of the leg does not typically line up with the anatomic axis or intramedullary canal. The mechanical axis includes a line from the center of a proximal joint to a distal joint of a long bone (e.g., femur or tibia), such that the mechanical axis is straight as it is a direct path between joint centers. The intramedullary generally follows the curvature of the femur, such that it is not straight as compared to mechanical axis.
Cut guides can be used to guide a saw and achieve the proper angle and position of the cuts performed during a TKA. Cut guides can be in the form of a guide member having slots therein for receiving and guiding the saw. In use, the guide member can be positioned against the bone with the assistance of positioning or alignment equipment. The proper positioning of such guide members is crucial to forming well-positioned bone cuts for attachment of the prosthetic femoral and tibial implant components. For example, the tibial cut affects spacing, alignment and balance between the tibia and femur when the knee is in flexion, and alignment and balance between the tibia and femur when the knee is in extension, as well as all points of articulation between extension and flexion. Once properly positioned and aligned, the guide member can be secured to the bone using bone pins or other securement means. For example, the guide member can be slidably mounted to an alignment guide, which can be mounted at an angle relative to an extramedullary guide or intramedullary rod. For an extramedullary tibial resection, an extramedullary guide can be located relative to the patient's anatomy to provide proper alignment relative to the tibia, and a guide member can be positioned on the proximal end of the tibia. Similarly, in an intramedullary tibial resection, an intramedullary rod can be inserted into a pre-drilled hole in the intramedullary canal of the tibia to provide anatomic alignment with a cut guide positioned on the proximal end of the tibia. For preparation of the femoral resection, an intramedullary rod can be positioned such that it extends across the distal end of the femur, and the cut guide can be positioned on the proximal end of the femur. The cut guide can be slid toward or away (medially-laterally) from the tibia or femur until it is properly positioned against the surface of the bone. The cut guide can then be secured to the bone with pins. The cut guide can be connected to the alignment guide using a pin/hole connect mechanism.